CODEWITHSUNDEEP
androidopencvimage-processingkalman-filter
Tony
Tony

Reputation: 111

Object track with Kalman filter

I want to implement a Kalman filter to track a point , here is my code 

    public Mat onCameraFrame(CvCameraViewFrame inputFrame) {        
    mRgba = inputFrame.rgba();
    mGray = inputFrame.gray();      

    switch (viewMode) {

    case VIEW_MODE_ColorDetect:


            /**
             * 
             * some code for color detect 
             * 
             */

            int ObjectCenterX = (int)((mboundingRect.tl().x + mboundingRect.br().x) / 2);
            int ObjectCenterY = (int)((mboundingRect.tl().y + mboundingRect.br().y) / 2);

            //get the object center point , and I whant to track it by kalman filter.
            Core.circle(mRgba, new Point(ObjectCenterX, ObjectCenterY), 5, ColorGreen, 2);


            /***********************************************Kalman************************************************************/
            try {                   
                Mat ObjectPoint = new Mat(1, 2, CvType.CV_32F);
                int[] PreObjectCenter = {ObjectCenterX, ObjectCenterY};
                ObjectPoint.put(0, 0, PreObjectCenter[0]);
                ObjectPoint.put(0, 1, PreObjectCenter[1]);
                ObjectPoint = myKalmanFilter(ObjectPoint);

                /**Question 2: How to get corrected point from Mat?**/

            } catch (Exception e) {
                Log.e("In camera fram: ", e.toString());
            }
            /*****************************************************************************************************************/

        }
     return mRgba;



return mRgba;
}

private Mat myKalmanFilter(Mat objectPoint){
    KalmanFilter KF = new KalmanFilter();
    try {
        KF.predict(objectPoint);

        KF.correct(objectPoint);
    } catch (Exception e) {
        Log.e("myKalmanFilter: ", e.toString());
    }

    return objectPoint;
}

I have 2 question , Q1. I got the following error for this code :

17:44:22.727: E/cv::error()(24902): OpenCV Error: Assertion failed (type == B.type() && (type == CV_32FC1 || type == CV_64FC1 || type == CV_32FC2 || type == CV_64FC2)) in void cv::gemm(cv::InputArray, cv::InputArray, double, cv::InputArray, double, cv::OutputArray, int), file /home/reports/ci/slave_desktop/50-SDK/opencv/modules/core/src/matmul.cpp, line 711 17:44:22.727: E/org.opencv.video(24902): video::predict_10() caught cv::Exception: /home/reports/ci/slave_desktop/50-SDK/opencv/modules/core/src/matmul.cpp:711: error: (-215) type == B.type() && (type == CV_32FC1 || type == CV_64FC1 || type == CV_32FC2 || type == CV_64FC2) in function void cv::gemm(cv::InputArray, cv::InputArray, double, cv::InputArray, double, cv::OutputArray, int) 17:44:22.727: E/myKalmanFilter:(24902): CvException [org.opencv.core.CvException: cv::Exception: /home/reports/ci/slave_desktop/50-SDK/opencv/modules/core/src/matmul.cpp:711: error: (-215) type == B.type() && (type == CV_32FC1 || type == CV_64FC1 || type == CV_32FC2 || type == CV_64FC2) in function void cv::gemm(cv::InputArray, cv::InputArray, double, cv::InputArray, double, cv::OutputArray, int) 17:44:22.727: E/myKalmanFilter:(24902): ]

Q2. After revise the code that it can work , how to get the x and y point from Mat?

EDIT: I still don't know how to set KalmanFilter dimensions , I set like this private KalmanFilter KF = new KalmanFilter(1, 2, 16, CvType.CV_32F); and eclipse show

Thread [<1> main] (Suspended (exception UnsatisfiedLinkError))
KalmanFilter.(int, int, int, int) line: 72
Tutorial1Activity.() line: 65 Class.newInstanceImpl() line: not available [native method] Class.newInstance() line: 1319
Instrumentation.newActivity(ClassLoader, String, Intent) line: 1069 ActivityThread.performLaunchActivity(ActivityThread$ActivityClientRecord, Intent) line: 2258
ActivityThread.handleLaunchActivity(ActivityThread$ActivityClientRecord, Intent) line: 2387 ActivityThread.access$600(ActivityThread, ActivityThread$ActivityClientRecord, Intent) line: 151
ActivityThread$H.handleMessage(Message) line: 1331
ActivityThread$H(Handler).dispatchMessage(Message) line: 99 Looper.loop() line: 155 ActivityThread.main(String[]) line: 5485
Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method]
Method.invoke(Object, Object...) line: 511
ZygoteInit$MethodAndArgsCaller.run() line: 1028 ZygoteInit.main(String[]) line: 795 NativeStart.main(String[]) line: not available [native method]

Upvotes: 1

Views: 1857

Answers (2)

Sergei S
Sergei S

Reputation: 3047

good example

Kalman Filter Implementation (Tracking mouse position)

http://opencvexamples.blogspot.com/2014/01/kalman-filter-implementation-tracking.html

Upvotes: -1

berak
berak

Reputation: 39796

  • please don't create a new KalmanFilter for each prediction/correction , it has to keep state for the whole duration of your program to work.

  • you need to create the KalmanFilter with correct dimensions for measurement size an dynparamsize, calling the empty constructor will give the above error.

  • KF.predict(objectPoint) will overwrite the contents in objectPoint, so you're correcting with the predicted value, not with your measurement. either use 2 different Mats there, or reverse the predict/correct order

  • unfortunately, the opencv java wrapper don't allow you to set statePre or transition Mats for the Kalman filter. it's current interface is a bit unusable. you'll either need jni to set them, or use the javacv bindings ( which are shabby outdated, but at least handle this part better )

Upvotes: 2

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